Air-compressor.



H. BOLTHOFF.

AIR COMPRESSOR.

APPLICATION FILED JULY 29. 1916.

Patented Nov. 18, 191?.

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avwcnroz- H. BOLTHOFF.

AIR COMPRESSOR.

APPLICATION FILED JULY 29.12am.

Patented Nov. 13, 1917.

3 SHEETS-SHEET 2.

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H. BOLTHOFF.

AIR COMPRESSOR.

- APPLICATION FILED JULY 29.1916.

1,246,801 Patented Nov. 13, 1917.

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HENRY BOLTHOFF, OF DENVER, COLORADO.

AIR-COMPRESSOR.

Specification of Letters Patent. Paiggnted N 13 191'?" Application filed July 29, 1916. Serial No. 112,031.

T 0 all whom it may concern:

Be it known that I, Hnxnv BoL'ri-iorr, a citizen of the United States, residing at the city and county of Denver and State of Colorado, have invented certain new d useful Improvements in rriuCompressors; and I do declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art .to which it appertains to make and use the same, reference being had to the accompanying drawings, and. to the characters of reference marked thereon, which form a part of this specification.

My i vention relates to improvements in air compressors, my object being to provide a construction of this class which shall be exceedingly eflicient in use as compared with the cost of operation. My further object is to provide a construction which shall be simple in its mechanism, and, ther fore, economical to construct.

In my improvement I employ two com pressor cylinders provided with reciprocating pistons, having cross heads suitably connected to cause the pistons to work in unison, the compression strokes occurring alternately. The compression in these cylinders is brought about by the inward movement of the pistons in both cylinders, consequently, while one piston is acting to compress the air, the piston of the other cylinder is receding and drawing in a charge of air through a check valve, preparatory to compression. The inner extremity of each cylinder is equipped with a valve which is opened at predetermined intervals for the purpose of allowing the compressed air to enter a centrally arranged receiver which is located between the two compression cylinders. An important feature of invem tion consists in the mechanism whereby the valves which control the discharge of compressed air into the receiver are opened to permit this discharge.

The mechanism for opening these valves is operated from a bar which connects the two cross heads, and is slidably mounted in guides arranged above the cylinders and forming an integral structure therewith. This bar which reciprocates in said guides and carries the cross heads with which the pistons are formed integrally, also carries a horizontally disposed arm which is connected with the upper extremity of a member including a sleeve, which is slldable on a stationary support, and carries at its lower extremity a pawl or rocking lever, which, as the pistons reciprocate, also reciprocatcs and is arranged to act upon lever arms which are connected in operative relation with the respective valves which control the discharge of air into the receiver through ports in the inner extremities of the compression cylinders, as heretofore explained. These valves are normally held in the closed position by means of a vertically disposed spring-actuated rod, whose upper extremity is pivotally connected ith the center of link, the opposite extremities of the link being pivotally connected with crank arms which are connected with spindles, which in turn are connected in operative relation with the stems of the said valves.

By virtue of this construction I am able, at the expenditure of a small amount of power, to open the valves which control the discharge of compressed air into the receiver at properly timed intervals. By virtue of this construction and arrangement for mechanically opening these valves, I avoid the expenditure of a great deal of power which would otherwise be necessary in forcing these valves open against the resistance of the air in the receiver. In the event that the air in the receiver is under approximately 100 pounds compression, and assuming that the difference in area between the opposite surfaces of each of these valves is several square inches, there would be considerable resistance to be overcome by the action of the piston. By employing my mechanical construction for opening these valves, I thus save considerable power, which enables me to economize in cost of operation.

Having briefly outlined my improved construction I will proceed to describe the same in detail, reference being made to the accompanying drawing in which is illustrated an embodiment thereof.

In this drawing Figure 1 is a vertical longitudinal section taken through my improved air compressor, cutting the cylinders, pistons, cross heads and the receiver.

Fig. 2 is a fragmentary side elevation of the structure, showing the central portion thereof where the valve controlling mechanism is located.

Fig. 3 is a cross section taken on the line 33, Fig. 2, looking toward the right.

Fig. at is a fragmentary elevation of the structure which acts to open the valves for controlling the passage of compressed air to the receiver, the parts being shown on a larger scale. This view is obtained by looking at Fig. 3 in the direction of arrow 4.

Fig. is. a View of the same structure. looking in the direction of arrow 5, Fi 4.

Fig. 6 is a sectional view of a friction block which coiiperates with a movable shoe forming a part of the valve opening mechanism.

Fig. 7 is a top view in detail of anothe feature of the valve opening mechanism.

Fig. 8 is a section taken on the line 8 8, Fig. 2, looking toward the left.

The same reference characters indicate the same parts in all the views.

Let the numeral 5 desi nate a suitable framework upon which are mounted in any suitable manner, two cylinders 6 and 7 connected by receiver 4, which is arranged between the cylinders and adapted to receive compressed air through ports 8 and 9 formed in the heads 10 and 12 of these cylinders, the said ports being controlled by valves 13 and 14, which are beveled, whereby their outer surfaces are of greater area than their inner surfaces. Since these valves open inwardly with reference to the receiver in order to properly perform their function, they are respectively equipped with horizontally disposed stems l5 and 16, which are slidable in suitable casings 17 and 18, their inner extremities being respectively equipped with brackets 19 and 20 which are vertically slotted to receive projections 21 and 22 formed on crank arms 23 of spindles 24, which are journaled in brackets 25, and also in the frame work 5 of the structure. These spindles are provided with beveled shoulders 26 which engage seats 27 to limit the endwise movement of the spindles in an outward direction. The outer extremities 28 of these spindles engage flat heads 29 of adjusting screws 30, which are threaded in the brackets 25, whereby the endwise thrust of the spindles against the shoulders 27 may be r lieved. WVhen the machine is in operation, it will be understood that the inner extremities of the spindles are exposed to the pressure of the air in the receiver4, hence there will be considerable pressure on the spindle in an outward direction, and without some means for relieving the pressure of the shoulder 26 on the seat 27 undue resistance or friction would result, and to some extent increase the wear upon the parts, and would also retard freedom of movement of the spindle in its bearings.

These spindles 24, while they are journaled in the frame 5 and brackets 25, have parts 31 which are preferably polygonal or square in cross section, and which engage openings of corresponding shape formed in hubs 32, which carry arms 33 and 34 which extend upwardly from the spindles, and are equipped with angle shaped wearing parts and 36, which are adapted to be engaged by off-set wearing parts 37 and 38, with which the extremities of a pawl or lever 39 are equip Jed, this pawl passing through an opening 40 formed in the lower extremity of a bracket 41 having a sleeve 42 mounted to slide on a stationary guide rod 43. This pawl or lever is arranged below the sleeve and is perforated, as shown at 44, to receive the pin 45 of an upwardly projecting arm 46, which is recessed, as shoWn at 47 to receive the depending projection 48 of a shoe 49, whose upper surface is curved to conform to the curve of a friction member 50 set into the face of a block 51, said face being curved to conform to the structure of the shoe. This block 51 is secured to an upward projection 5-3 of the bracket 41, this projection having a reduced pin 54 which passes through an opening formed in the outer extremity of a horizontally disposed arm 55, whose inner extremity is secured to the bar 56, which is slidable in guides 67, and carries cross-heads 68 and 69 which are equipped with pistons 70 and 71, which reciprocate in the cylinders 6 and 7.

In the lower portion of the recess 47 of the part 46 is located a spiral spring 72, which acts upon the extremity of the pin 48 of the shoe 49 to cause the shoe to engage the friction face 50 of the block 51 with sufficient pressure to enable the shoe to properly perform its function, as hereinafter explained.

The pawl 39 through which the pin 45 passes, is made fast to said pin by means of a set bolt 73. Furthermore the pin 45 is journaled in the lower portion 74 of the bracket 41 on opposite sides of the pawl 39.

The opposite extremities of the pawl 39 are further equipped with of -ets 75 and 76, which are adapted to engage beveled parts 77 and 78 mounted near the extremities of the stationary rod 43. As the bracket 41 is moved in opposite directions due to the reciprocation of the carrier bar 56, the offsets 75 and 76 are respectively and alternately brought into engagement with the evels 77 and 78, whereby the pawl 39 is tilted or rocked to cause one of its extremities to be slightly lower than the other, and in such position that the adjacent wearing off-set 37 or 38, as the case may be, willact upon the upper extremity of an arm 33 or 34, whereby the latter is actuated sufiiciently to operate the spindle 24 and its crank arm 23, whereby one of the valves 13 or 14 is opened as the piston 70 or 71 approaches its inward limit of movement.

As the pawl 39 is acted on by the bevel 77 or 78, as the case may be, whereby a slight rocking movement. is imparted to the pawl,

a corresponding movement is imparted to the pin 45 of the member 46, since the pawl 39 is fast on the pin 45, with the result that the shoe 49 is shifted on the friction face 50 of the block 51, and this engagement of the shoe with the block will maintain the pawl normally in the adjusted position a sufficient length of time to enable the pawl to act upon the arm 33 or 34 for valve opencollar 83 fast on the rod, the spring 81 being normally under tension or compresslon to exert the desired stress on the rod. The upper extremity of the rod is pivotally connected, as shown at 84, with the center of the link 80, while the opposite extremities of the link are pivotally connected, as shown at 85 and 86, with the adjacent extremities of crank arms 87 and 88, whose outer extremi ties are respectively made fast to the adjacent ends of the spindles 24. These crank arms are so arranged with reference to the link 80 that the upward stress on the rod 79, imparted by the spring 81 acts upon the spindles 24 to normally maintain the two valves 13 and 14 in the closed position. It is evident, however, that as one arm 33 or 34 is actuated by the pawl 39, the movement of said arm will serve to unseat the corresponding valve, since each spindle 24 acts as a rock shaft upon which an arm 87 and '88, and an arm 33 or 34 are made fast. In other words, the movement of these arms serves to impart the necessary partial rotation to the spindles 24 to unseat the said valves through the medium of the cranks 2 at the inner extremities of the said spindles.

Preparatory to describing the operation of the machine, it should be explained that the pistons and 71 are reciprocated through the medium of a piston rod 89 which projects into a cylinder 90 containing a fluid actuated piston (not shown). The rod 89 is reciprocated in the usual manner where steam or other motive fluid is employed to act alternately upon the opposite ends of a piston, to which the rod 89 is attached. As this mechanism is old and nothing is claimed thereon in this application, it is not shown in detail. From this it "will be understood that any suitable power I may be employed to impart the reciprocating movement to the pistons 70 and 71 in the cylinders 6 and 7. As shown in the drawing (see Fig. 1), a fly wheel 91 is fast on a shaft 92, which is equipped with a crank wheel 93, with which one extremity of a rod 94 is connected, as shown at 95, at a suitable point beyond the center of the wheel. The opposite extremity of this rod 94' is connected, as shown at 96, with a wrist pin with which the piston 70 is provided. It is evident that the shaft 92 might be made the operating shaft for the air compressor, in which event power could be applied thereto from a motor of any suitable construction.

From the foregoing description, the use and operation of'my air compressor will be readily understood. Assuming that the piston 71 (see Fig. 1) is traveling toward the left, while the piston 70 is traveling in the same direction, the piston 71 will be approaching the valve 14 and compressingair within the cylinder 7, while the piston 70, by virtue of a spring actuated check valve 97 therein will be opened to allow a charge of air to enter the cylinder 6. When the piston 71 has nearly reached its inward limit of movement toward the valve 14, the off-set 38 of the pawl 39 will act upon the upper extremity of the arm 33 and rock the corresponding spindle 24 sufficient y to open the valve 14 and allow the charge of ,air

compressed in the cylinder 7 to enter the receiver 4. As soon as this occurs, the piston 71 having reached its limit of movement toward the left, the two pistons will begin movement in the opposite direction. In thisevent the piston 70 will begin to compress the charge of air in the cylinder 6, while a spring actuated check valve98 of the piston 71 will open to allow a charge of atmospheric air to enter the cylinder 7 It should be explained that the outer extremities of both cylinders 6 and 7 are open to the atmosphere. As the pistons 7 O and 71 were moved toward the left, being carried by the beam 56, the latter in turn carrying the pawl 39, the off-set of this pawl was brought into engagement with the bevel 7 7 whereby the pawl was tiltedto bring its off-set 37 into position to engage the upper extremity of the arm 34 during the movement of the pistons toward the right. During the engagement of the off-set 75 with the bevel 77 and the movement of the pawl 39, as just explained, the shoe 49 will be moved on the friction face 50 of the block 51 a corresponding distance, and the friction between the shoe and the block will maintain the pawl in the adjusted position, consequently in such a position that its ofi-set 37 will engage the upper extremity of the arm 34 as the pistons approach their limit of movement toward the right and open the valve 13 to allow the compressed air from the cylinder 6 to enter the receiver 4. It is evident that as soon as either piston, after completing its compression stroke, begins to move in the opposite direction, the pawl 39 will be disengaged from the arm 33 or 34, as the case may be, in which event the spring actuated rod '79 will act to close'the valve 13 or 14,

as the case may be. It will also be understood .that when either of the arms 33 or 34 is acted on by the pawl 39 to open one of the valves 13 or 14, the rod 79 is moved downwardly whereby the spring 81 is placed under further tension. At the same time the stress upon one extremity of the link 80 will act upon the opposite extremity of the link to place increased closing pressure upon the opposite or closed valve 13 or 14:, as the case may be.

It should be explained that the opening movement of the valves 13 and '14 is so timed that it occurs when the pressure in the adjacent extremities of the cylinders is approximately the same as that in the receiver, thus avoiding-the necessity of an appreciable excess of pressure in the cylinders over that in the receiver. 7

On the contrary, if these valves were opened by the pressure in the cylinders or in the ordinary manner, the excess of pressure in the cylinders over that in the re ceiver would be considerable since the difference in area between the receiver surfaces of the valves and the cylinder surfaces of these valves, is several square inches, and this excess pressure must be developed in the cylinders before the valves would open, whereby a corresponding increase in power for opening purposes would be required, thus adding considerably to the cost of operating.

Having thus described my invention, what I claim is:

1. An air compressorcomprising two cyl inders, a receiver located between the cylinders, pistons in the cylinders, a bar connecting the pistons tocause them to move in unison inethe cylinders, the heads of the cylinders adjacent the receiver having ports,

valves for controlling.saidports and adapt ed to open inwardly, and means connected withthe said valves within the receiver and adapted to cooperate with the said piston connecting rod wherebythe said valves are operated at properly timedintervals.

2. An air compressor comprising two cylinders, a receiver arranged between thetwo cylinders, pistons in the cylinders, the heads 7 of the cylinders having ports which communicate with the receiver, valves for controlling said ports and adapted to open into the receiver, a bar connecting the pistons to cause them to move in unison, an operative connection between said bar and the alves'for operating the latter at properly tnned intervals, said connection including a pawl carried by the bar.

3. An air compressor comprising two cylinders, a receiver arranged between the cylinders, the heads of the cylinders having ports connnunieating with the receiver, valves for controlling said ports, a bar connecting the pistons to cause them to move in unison in the cylinders, an operative connection between said bar and the valves for opening the latter at predetermined intervals, said connection including a pawl carried by the bar and slidably mounted to have a limited rocking movement. 7

4. An air compressor comprising two cylinders, a receiver arranged between the cylinders, pistons in the cylinders, the heads of the cylinders adjacent the receiver having ports, valves controlling said ports and adapted to open into the receiver, a bar connecting the pistons to cause them to move in unison in the cylinders and an operative connection between said bar and the valves for opening the latter at pre-determined in tervals, said connection including spindles connected at their inner extremities withthe valves, their outer portions being equipped with crank arms, spring-held in the valve closing position, and a pawl mounted to perand rocking movement to brlng its extremities .into position to act alternately on the said crank arms during the reciprocation of the pistons.

5. An air compressor comprising two cylinders, pistons therein, a receiver between the cylinders, the heads of the cylinders having ports communicating with the receiver, valves for controlling said ports and normally spring-held in the closed position, a bar connecting the pistons to cause them to move in unison, a bracket slidably mounted and connected to reciprocate with the bar, a pawl carried by the bracket and mounted to have a rocking movement, means acting on the pawl to tilt the same as the latter reaches its limit of movement in either direction, means also mounted on thebracket for frictionally retaining the pawl in the adjusted position, and means connected in operative relation with the valves to open the latter at properly timed intervals.

6. An air compressor comprising two cylinders, pistons therein, a receiver between the cylinders, the heads of the cylinders having ports communicating with the receiver, valves for controlling said ports and normally spring-held in the closed position, a bar connecting the pistons to cause them to move in unison, a bracket slidably mounted and connected to reciprocate with the bar, a pawl carried by the bracket and mounted to have a rocking movement, means acting. on the pawl to tilt the same as the latter reaches its limit of movement in either direction, means also mounted on the bracket for frictionally retaining the pawl in the adjusted position, and means connected in operative relation with the valves for opening the same at properly timed intervals, said means including spindles having crank arms connected with the respective valves, and other crank arms arranged to be directly acted on ,by the pawl.

7. An air compressor comprising two cylinders, a receiver between the cylinders, pistons in said cylinder, ports in the cylinder heads communicating with the receiver, valves for controlling said ports, means for opening said valves including spindles having crank arms connected with the valves, and also other crank arms, a link connecting the latter, and a spring actuated rod connected with the link for normally holding the valve in the closed position.

8. An air compressor comprising two cylinders, a receiver between the cylinders, pistons in said cylinders, ports in the cylinder heads communicating with the receiver, valves for controlling said ports, spindles having crank arms connected with the valves, and also other crank arms, a link connecting the latter, a spring actuated rod connected with the link for normally holding the valves in the closed position, and an operative connection between thepistons and said spindles for automatically opening the valves at properly timed intervals.

9. An air compressor comprising two cylinders, a receiver between the cylinders, pistons in said cylinders, ports in the cylinder heads communicating with the receiver, valves for controlling said ports, spindles having crank arms connected with the valves, and also other crank arms, a link connecting the latter, a spring actuated rod connected with the link for normally holding the valves in the closed position, and an operative connection between the pistons and said spindles for automatically opening the valves at properly timed intervals, said means comprising crank arms on the spindles, a bar connecting the pistons, and means carried by the bar and acting alternately on said crank arms to perform the aforesaid function.

In testimony whereof I affix my signature.

HENRY BOLTHOFF.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. C. 

